1. Field of the Invention
The present invention relates to an electronic device mounted on a vehicle. Such as an electronic device, there are various sensors and a control unit installed in an engine room. More particularly, the present invention is relates to the configuration of sealing various sensors and to the configuration of sealing the control unit. Various sensors have sensing elements for detecting various physical quantities and electrical circuits for controlling the sensing elements, and output various quantities as electrical signals. The control unit has a microprocessor that controls various states of a vehicle in response to electrical signals of the sensors.
2. Prior Art
An example of the sealing configuration of the above-mentioned type is found in the thermal type flow meter disclosed in Japanese Application Patent Laid-Open Publication No. Hei 06-11373. This type of the configuration is used in physical quantity detecting apparatus and controller in engine room.
It will be described below using an example of the thermal type air flow meter in the Japanese Application Patent Laid-Open Publication No. Hei 06-11373. These physical quantity sensors are used under the severe environmental conditions of high temperature, low temperature and high humidity. The air flow sensor has members formed by the so called insert-molding with resin, wherein the terminal for holding the heating resistor and thermo sensitive resistor and the base made of aluminum characterized by excellent thermal conductivity are inserted in said molded member. The drive circuit for receiving electrical signals of the heating resistor and the thermo sensitive resistor and for outputting them to the outside control unit is bonded to the base. The drive circuit is installed in the case made of resin. In this sealing configuration, the cover for covering the case is bonded to the upper surface of the case. Silicone adhesive is mainly used for connection between the drive circuit and the base, and is also used in many cases for connection between the base and the case. Further, epoxy adhesive or silicone adhesive is used for connection between the case and cover.
A silicone component which contains antibacterial and mildew-proof in silicone adhesive is disclosed in Japanese Application Patent Laid-Open Publication No. Hei 07-62242, wherein the silicone composition is mixed with Zeolite containing 0.1 to 15 wt % silver ion.